Smelting process for eliminating phosphorus



Patents Nov. 24, 1931 UNITED, STATES PATENT OFFICE WILLIAM C. READ, OF SCARSDALE, NEW YORK, ASSIG -NOR '1'0 ELECTRO METALLURGIC COMPANY, A CORPORATION OF WEST VIRGINIA A SMEL'IIN G PROCESS FOR ELIMINATING PHOSPKOBUS No Drawing. Application filed April 3,

. smelting high-phosphorus ores and concentrates of the metals under discussion. By the use of the invention it is possible economically to recover the metal values as an alloy in which the ratio of percentage of valuable metal to percentage of phosphorus is much higher than in the material smelted. It will of course be understood that in some of the processes used in concentrating these ores the chemical composition of the ore is changed,

as where sodium vanadate is formed from vanadium ores. The invention is applicable to such chemical concentrates aswell as to other types of concentrates, and to unconcentrated ores having a sufficiently high metal content.

The process is carried out by smelting the ore or concentrate with an excess of silicon in the presence of a basic slag. The silicon used in the reduction may be in the commercially pure form (so-called silicon metal), or in the 05 to the charge. The excess of reducing agent form of commercial ferrosilicon. If the reducing agent and the ore do not together contaln as much as is to be present in the reduced metal, more iron can of course be added should be such that the alloy produced will contain at least about 10% of Si, and percentages up to 30% and even higher give 'good results. The ore and the silicon-con- 40 taining metal are preferably ground or crushed, and mixed together and with the basic flux, the mixture being charged into a suitable electric furnace for smelting.

Lime is the preferred base. Excellent phosphorus elimination has been obtained 1930. Serial No. 441,426.

when the base-to-acid ratio in the slag was approximatel 2. A typical slag had the followmg ana ysis:

. Per cent CaO 60.28 M 0 4.80 S102 The base-to-acid ratio of this slag, calculated in the usual way, is 1.95. Slags with ratios of 3 or more have also been used successfully. Such slags as those which have been ment oned have no objectionable features, and since they are very effective the lowest basicities which can be used have not been investigated. However, my experience with the process leads me to believe that slags having a ratio of less than unity will not ive acceptable results in most cases, and do not recommend them.

The invention may be applied to any of the tungsten ores or concentrates, and is especially valuable for the working of ores of the iron-tungsten class, such as ferberite ores,

and to the calcium-tungstate ores such as the 7 scheelites, since these ores, and particularly the former class, often carry much phosphorus.

In a particular run the charge was made up as followsi Parts Ferberite ore 200 Silicon metal 116 Lime 270 The ore contained 26;34% W and 0.264% P, the ratio P being 100. The alloy produced analyzed:

Per cent W 30.38 Si 29.35 P 0.013

with the balance mostlyiren. Tn the alloy, the ratio T P exceeded 2300.

In another run the charge was as follows:

larts Scheelite ore 196 Silicon metal 88 Steel scrap v15 9 Lime 200 The ore contained 52.94% W and 0.085% P. The alloy produced analyzed: 7

Per cent W 55. 79 Si 26. 55 P 0. 010

The elimination of 90-95% of the phosphorus contained in the ore is usual.

The following example illustrates the invention as applied to a high-phosphorus sodium molybdate. The charge consisted of The charge was divided into three batches and smelted in an electric furnace lined with magnesia materials. The slag was tapped off after each batch of mixture had been furnaced, and the alloy was allowed to solidify on the hearth. When cool the alloy was removed, cleaned and crushed. Its analysis was as follows:

Mo 18. 50 per cent S1 29. 4-1 per cent P Trace Balance Largely iron Ratio over 2000 The slag contained:

Per cent GaO 60. S10 29. 50

The elimination of phosphorus was substantially complete. It will be 'iioted that the base-to-acid ratio in the slag was higher than 2.

Less

The following example illustrates the invention as applied to a high-phosphorus sodium vanadate. The charge consisted of:

Parts Sodium vanadate 200 Silicon metal 120 Ferrosilicon (59% Si) 30 Lime 550 Fluorspar 35 The sodium vanadate analyzed:

Percent V 9. 74 P 0. 2t

V Ratlo -40 The charge was smelted in a magnesia-lined electric furnace and yielded products of the following composition:

Alloy Per cent V 23. 20 Si 33. 08 Fe 37.75 P 0. 058

Slag Per cent CaO 52. 28 Si() 28. 9

V Ratlo -400 Less than 9% of the phosphorus present in the sodium vanadate entered the ferrovanadium. The ratio of base to acid in the slag is higher than 2 when the soda from the sodium vanadate and the magnesia dissolved from the furnace lining are taken into account.

The allo produced in any of the foregoing examp es may be used without further treatment or it may be furnaced with a low phosphorus ore containing one or more of the metals present in the alloy, or with mill scale or other oxidizing agent in accordance with methods well known in the art to remove silicon and roduce a commercial ferroalloy low in silicon and phosphorus.

This application contains matter disclosed in my pending application Serial No. 264,959, filed March 26, 1928.

I claim 1. Process of recovering a metal of the group consisting of tungsten, molybdenum and vanadium by smelting a high phosphorus ore or concentrate of such metal which comprises mixing the ore or concentrate with a metal rich in silicon and heating the mixture to a smelting temperature in the presence of a lime slag having a base-to-acid ratio at least about 2, the proportion of silicon used being sufficient to reduce the ore or concentrate and give a reduction product containing at least 10% Si.

2. Process of smelting phosphorus-contaminated tungsten ores or concentrates which comprises mixing the ore or concentrate with a metal rich in silicon and heating 5 the mixture to a smelting temperature in the presence of a lime sla having a base-to-acid ratio at least about 2, t e proportion of silicon used being sufiicient to reduce the ore or concentrate and give a reduction product con- 10 taining at least 10% Si.

In testimony whereof, I afiix my signature.

WILLIAM G. READ. 

